A drive device of an electric vehicle in which an electric motor, which is a drive source of the electric vehicle, and a portion of the harness extended from the motor to a power supply, that is, a battery are accommodated in a swing arm supported by a vehicle body frame to freely swing in the up and down direction is known. Japanese Patent No. 4188641 discloses an electric vehicle in which the front portion of a rear arm (i.e., swing arm) is swingably supported by the vehicle body frame, the motor and a power unit or an electrical component are incorporated in the back portion of the rear arm, and a harness for connecting the power unit and an external battery is held by the rear arm. The rear arm described in Japanese Patent No. 4188641 includes a first member for accommodating the power unit and the harness and extending in a front and back direction of a vehicle body, a second member coupled to the side at the back part of the first member and interiorly including a motor, a third member coupled to the side at the front part of the first member and configuring a pivotally supporting portion (pivot portion) of the rear frame in the vehicle body frame with the first member, and a cover, positioned between the second member and the third member, for covering the first member. The harness is pulled out to the outside through a through-hole formed at the joint portion of the first member and the third member.